This invention relates to synchronizing databases.
Databases are collections of data entries which are organized, stored, and manipulated in a manner specified by applications known as database managers (hereinafter also referred to as "Applications"; the term "database" will also refer to the combination of a database manager and a database proper). The manner in which database entries are organized in a database is known as its data structure.
There are generally two types of database managers. First are general purpose database managers in which the user determines (usually at the outset, but subject to future revisions) what the data structure is. These Applications often have their own programming language and provide great flexibility to the user. Second are special purpose database managers that are specifically designed to create and manage a database having a preset data structure. Examples of these special purpose database managers are various scheduling, diary, and contact manager Applications for desktop and handheld computers. Database managers organize the information in a database into records, with each record made up of fields. Fields and records of a database may have many different characteristics depending on the database manager's purpose and utility.
Databases can be said to be incompatible with one another when the data structure of one is not the same as the data structure of another, even though some of the content of the records is substantially the same. For example, one database may store names and addresses in the following fields: FIRST.sub.-- NAME, LAST.sub.-- NAME, and ADDRESS. Another database may, however, store the same information with the following structure: NAME, STREET.sub.-- NO., STREET.sub.-- NAME, CITY.sub.-- STATE, and ZIP. Although the content of the records is intended to contain the same kind of information, the organization of that information is completely different.
Often users of incompatible databases want to be able to synchronize them with one another. For example, in the context of scheduling and contact manager Applications, a person might use one Application on the desktop computer at work while another on his handheld computer or his laptop computer while away from work. It is desirable for many of these users to be able to synchronize the entries on one with entries on another. The U.S. patent and copending patent application of the assignee hereof, Puma Technology, Inc. of St. Jose, Calif. (U.S. Pat. No. 5,392,390 (hereinafter, "the '390 patent"); U.S. application Ser. No. 08/371,194, filed on Jan. 11, 1995, incorporated by reference herein) show two methods for synchronizing incompatible databases and solving some of the problems arising from incompatibility of databases.
Synchronization of two incompatible databases often requires comparison of their records so that they can be matched up prior to synchronization. This may require transferring records in one database from one computer to another. However, if the data transfer link between the two computers is slow, as for example is the case with current infrared ports, telephone modem, or small handheld computers, such a transfer increases the required time for synchronization by many folds.